Recent studies have demonstrated a correlation between perceived stress and oxidative stress. As SOD is the main enzyme of the enzymatic antioxidant defence system of the body, we evaluated the effect of an oral daily intake of a proprietary melon juice concentrate rich in SOD (EXTRAMEL®) on the signs and symptoms of stress and fatigue in healthy volunteers.

Perceived stress, the main parameter of the study, was significantly decreased by Extramel® supplementation. Quality of life (general physical and mental health state, physical and social functioning, physical and emotional health, pain, and vitality) was also improved as shown by SF-36 Health Survey scale results.
Moreover, Extramel® supplementation clearly reduced physical and mental fatigue. It is important to note the Stroop score improvement (27.9%) after three months of treatment. Stroop test is considered to measure selective attention, cognitive flexibility, and processing speed, and is currently used as a tool in the evaluation of executive functions.

Comment Update

Link Between Oxidative Stress and Individual Stress

The link between individual stress and intracellular oxidative stress is now well-established. Indeed, Casado et al. have demonstrated in a clinical trial on nurses in an intensive care unit, a clear relationship between oxidative stress markers, in particular an increase of reactive oxygen species (ROS) production and malondialdehyde (MDA) levels, and occupational stress [1,2]. In the same way, Lucca et al. showed, on a rat model of depression, that individual stress induces oxidative stress (increase of lipid peroxidation) and an imbalance between antioxidant enzymes activities (superoxide dismutase (SOD) and catalase) that contribute to stress-related diseases like depression [3]. Finally, Maes et al. have shown that major depression is accompanied by a decrease in zinc, coenzyme Q10, vitamin E and antioxidant enzymes, and by an induction of oxidative and nitrosative pathways [4,5].

Oxidative stress is also involved in fatigue. Shichiri et al. have demonstrated an increase in oxidative stress markers in plasma of tired patients, who worked overnight [6]. Oxidative stress levels are also raised in chronic fatigue syndrome [7]. Indeed, Morris and Maes [8] have reviewed that chronic fatigue syndrome is accompanied by lowered zinc, and reduced glutathione and coenzyme Q10.

In summary, oxidative stress (increase in ROS and decrease of antioxidant defenses) is involved in psychological stress and related disorders.

In this context, it could be interesting to consider supplementation based on antioxidants as a possible strategy for improving stress and related disorders. An improvement in memory has been reported by Tagliari et al. in stressed rats treated with vitamins C and E [9]. Gupta et al. have shown that curcumin attenuates chronic fatigue syndrome in murine water immersion stress model [10]. Some human clinical studies have also demonstrated beneficial effects of antioxidants on stress and fatigue. For example, Yagi et al. have shown that supplementation with lutein could help to reduce symptoms of visual fatigue [11]. Oral administration of pyrroloquinoline quinone reduces stress, fatigue, and improves sleep [12].

Moreover, the influence of Extramel® (Bionov, Eyragues, France), a form of melon SOD, has been assessed in a first pilot study, during 28 days [13], in which beneficial effects have been shown.

The present clinical study aims to confirm the results of our earlier pilot study and know whether the daily intake of this SOD melon concentrate can reduce stress and fatigue in human patients over a longer period (84 days).